1. Field of the Invention
The present invention relates to a semiconductor laser device that is equipped with a semiconductor laser chip and is used as, for example, a light source of an optical pickup apparatus for an optical disk system, and also relates to a method for manufacturing the semiconductor laser device.
2. Description of the Related Art
FIG. 14 is a perspective view illustrating a configuration of a related art semiconductor laser device 1. The semiconductor laser device 1 disclosed in Japanese Unexamined Patent Publication JP-A 2002-232059 comprises: an island portion 4 that is a component made of metal including a reference face 2 and a block portion 3 protruding in a direction substantially perpendicular to the reference face 2; a lead 5; a resin portion 7 integrally formed with the island portion 4 and the lead 5 so as to fix a relative positional relation between the island portion 4 and the lead 5; a laser chip 8 fixed to the block portion 3; and a light receiving element 9 directly fixed to the resin portion 7. The laser chip 8 and the light receiving element 9 are covered with a cap 11 connected to the island portion 4 by resistance welding.
Further, in a semiconductor laser device disclosed in Japanese Unexamined Patent Publication JP-A 10-256649(1998), an island on which a laser diode chip and a light receiving element are mounted is made of resin, on which a lead pin is disposed in a skewered form. To the island is provided a cap that covers the laser diode chip and the light receiving element. The laser diode chip is fixed to the island via a monitoring photodiode.
In Japanese Unexamined Patent Publication JP-A 11-265956 (1999) is disclosed a cavity package, although not a semiconductor laser device, which comprises a package main body in which a metal lead frame is embedded; a semiconductor IC (integrated circuit) provided on the lead frame and bonded thereto by a bonding wire; and a lid made of the same thermoplastic material as that of the package main body and fused by ultrasonic fusing means for performing ultrasonic fusion on the package main body.
In the art disclosed in JP-A 2002-232059, the cap 11 is welded to the island portion 4 by resistance welding. In resistance welding, electric energy is converted into thermal energy to melt contact portions of metals, and the contact portions are pressurized and joined. Therefore, there is a possibility that the laser chip 8 fixed to the island portion 4 is heated via the island portion 4 having high thermal conductivity, which may cause a decrease of yield rate.
Since the island is made of resin in the art disclosed in JP-A 10-256649, there is no possibility that the laser chip is heated. However, since the island and the cap are fixed to each other by fitting or engaging, there is a need to provide the island and the cap with fitting portions or engaging portions. In the case of forming the fitting portions or engaging portions, there is a problem that it is difficult to make the device small and moisture or the like is easy to penetrate through a gap into the device. Moreover, it is also described to use an adhesive to fix the cap and island together with fixing by fitting or fixing by engaging. However, in the case of fixing the cap and island using the adhesive, there is a need to make a region to apply the adhesive, and hence, there is a problem that downsizing is hindered. Furthermore, since the laser diode chip is fixed to the island made of resin via the monitoring photodiode, and heat generated when the laser diode chip emits light is hard to be released, there is a problem such that life of the laser diode chip is shortened.
Further, in the art disclosed in JP-A 11-265956, by integrating the package main body and the lid by ultrasonic fusion, a need for forming the region to apply the adhesive required when connecting the package main body and the lid with the adhesive is eliminated, so that it is possible to downsize the device. However, the art disclosed in JP-A 11-265956 is not applied to a semiconductor laser device, and there is a problem that it is impossible to sufficiently release heat even if mounting a semiconductor laser chip in place of the semiconductor IC.